The invention relates to land vehicles, and, more particularly, those equipped with pollutant-free or pollution-controlling engines having an independent combustion chamber.
The author, in his published Patent Application WO 96/27737, described a method for the pollution control of an engine having an independent external combustion chamber, operating according to a bi-modal principle with two types of energy, using either a conventional fuel of the petrol or gas-oil type on the highway (mono-modal operation with air/fuel) or, at low speed, especially in urban and suburban areas, an addition of compressed air (or of any other non-pollutant gas), to the exclusion of any other fuel (mono-modal operation with air, that is to say with the addition of compressed air). In his French Patent Application 96/07714, filed on Jun. 17, 1996, now French Patent 2 749 882 the author described the installation of this type of engine operating mono-modally, with the addition of compressed air, on service vehicles, for example urban buses.
In this type of engine, in the air/fuel mode, the air/fuel mixture is sucked up and compressed in an independent suction and compression chamber. This mixture is then transferred, still under pressure, into an independent and constant volume combustion chamber, so as to be ignited there, in order to increase the temperature and pressure of the said mixture. After the opening of a transfer connecting the said combustion chamber to a depressurization and exhaust chamber, this mixture will be depressurized into the latter so as to carry out work there. The depressurized gases are subsequently discharged into the atmosphere through an exhaust pipe.
In low-power air operation, the fuel injector is no longer activated; in this case, a small quantity of additional compressed air, coming from an external reservoir where the air is stored under high pressure, for example 200 bar, and at ambient temperature, is introduced into the combustion chamber, substantially after the compressed air, without fuel, coming from the suction and compression chamber has been admitted into the said combustion chamber. This small quantity of compressed air, at ambient temperature, will heat up in contact with the high-temperature air mass contained in the combustion or expansion chamber and will expand and increase the pressure prevailing in the chamber, in order to carry out motive work during depressurization.
This type of bi-modal or bi-energy engine (air and petrol or air and additional compressed air) may also be modified for preferred town use, for example on all vehicles and, more particularly, on urban buses or other service vehicles (taxis, refuse lorries, etc.), in the air/compressed-air mono-mode, by omitting all the elements of the engine which operate with traditional fuel.
The engine operates, in mono-mode only, with the injection of additional compressed air into the combustion chamber which thus becomes a combustion chamber. Moreover, the air sucked in by the engine can be filtered and purified through one or more charcoal filters or filters using another mechanical or chemical method, a molecular sieve or other filters, in order to produce a pollution-controlling engine. The use of the term xe2x80x9cairxe2x80x9d in the present text refers to xe2x80x9cany non-pollutant gasxe2x80x9d.
In his French Patent Application 9611632, the author also described the installation of on-board high-pressure compressors for recharging with compressed air the reservoir of the vehicle equipped with engines, such as those described above, the compressor being driven by an autonomous motor with an autonomous energy source and being engaged on the transmission in order to operate and replenish the reserves of compressed air of the vehicle during slowing and braking, thus making it possible to recover considerable energy dissipated during these operations.
However, in this type of installation, the high-pressure and high-temperature compressed air fills the main reservoir which is substantially at ambient temperature and is cooled. This solution causes the loss of a large part of its energy, especially when the reservoir begins to empty, thus bringing about a loss of its pressure due to depressurization.
The method according to the invention proposes another solution which makes it possible, in addition, to make available an additional torque and an additional power reserve during accelerations. It is characterized by the means employed and, more particularly, in that, during decelerations and braking, the high-pressure compressor, which is activated by a clutch or any other coupler, then serves as a retarder, or even as a brake, by generating compressed air at a high pressure of, for example, 200 bar and at high temperature. This compressed air is diverted and stored in a reservoir, heat-insulated or not, called the reacceleration reservoir, where the compressed air is maintained at high temperature and high pressure, so as to be utilized as soon as the vehicle is put into action again, by being injected into the combustion chamber of the engine. This compressed air, which has thus preserved most of its temperature and pressure due to the short dwell time in the reacceleration reservoir, is reinjected, hot, into the combustion chamber of the engine and provides a considerably larger amount of energy when the vehicle is put into action again or restarted. The capacity of the heat-insulated reacceleration reservoir, as well as the pressure of the air contained in it, is provided according to requirements, and, when the reacceleration reservoir is full, the air is once again diverted towards the main reservoir.
The average person skilled in the art can calculate the volume and pressure of the reacceleration reservoir as a function of the average frequency and average intensity of the brakings and accelerations, depending on the intended use.
According to a preferred characteristic of the invention, the reacceleration reserve is produced in a variable-volume system, in order, as soon as it begins to be filled, to maintain the compressed air stored in it at a virtually constant pressure and temperature, by means of a device assisted by mechanical, pneumatic or hydraulic systems, such as springs or the like, and, more particularly, by means of a device utilizing the compressed air under pressure in the main reservoir, after the said air has been depressurized to a specific pressure. This variable-volume heat-insulated reacceleration capacity thus prevents the falls in pressure and temperature of the compressed air while it is being filled and makes it possible, at any moment, to have available a quantity of air at the desired high pressure and at high temperature, so as to make it possible to put the vehicle into action again, without waiting until the reacceleration capacity is filled completely in order to reach the desired service pressure (for example, 100 bar).
Thus, shortly after slowing or braking, when the vehicle driver wants to reaccelerate, a quantity of compressed air at high pressure and high temperature, extracted from the reacceleration capacity, is injected into the combustion chamber, making it possible to obtain very high pressures in the said chamber, these being tokens of torque and power.
Numerous means for maintaining the temperature in the reacceleration reservoir may be employed, and mention may be made, for example, of: the use of ceramic or of a heat-insulating method, such as glass wool or the like, and it is conceivable to produce non-polluting thermal or chemical heating systems, without thereby departing from the method according to the invention.